Lithium batteries are prepared from one or more lithium electrochemical cells containing electrochemically active materials. Such cells typically include an anode (negative electrode), a cathode (positive electrode), and an electrolyte interposed between spaced apart positive and negative electrodes. Batteries with anodes of metallic lithium and containing metal chalcogenide cathode active material are known. The electrolyte typically comprises a salt of lithium dissolved in one or more solvents, typically aprotic organic solvents. By convention, during discharge of the cell, the negative electrode of the cell is defined as the anode. Cells having a metallic lithium anode and metal chalcogenide cathode are charged in an initial condition. During discharge, lithium ions from the metallic anode pass through the liquid electrolyte to the active material of the cathode whereupon they release electrical energy to an external circuit.
It has recently been suggested to replace the lithium metal anode with an insertion anode, such as a lithium metal chalcogenide or lithium metal oxide. Carbon anodes, such as coke and graphite, are also insertion materials. Such negative electrodes are used with lithium-containing insertion cathodes, in order to form an electroactive couple in a cell. In order to be used to deliver electrochemical energy, such cells must be charged in order to transfer lithium to the anode from the lithium-containing cathode. During discharge the lithium is transferred from the anode back to the cathode. During a subsequent recharge, the lithium is transferred back to the anode where it re-inserts. Upon subsequent charge and discharge, lithium ions are transported between the electrodes. Such rechargeable batteries, having no free metallic species are called rechargeable ion batteries or rocking chair batteries. See U.S. Pat. Nos. 5,418,090; 4,464,447; 4,194,062; and 5,130,211.
Known positive electrode active materials include LiCoO2, LiMn2O4, and LiNiO2. The cobalt compounds are relatively expensive and the nickel compounds are difficult to synthesize. A relatively economical positive electrode is LiMn2O4, for which methods of synthesis are known. The lithium cobalt oxide, the lithium manganese oxide, and the lithium nickel oxide have a common disadvantage in that the charge capacity of a cell comprising such cathodes may suffer a significant loss in capacity. That is, the initial specific capacity available (milliamp hours/gram) from LiMn2O4, LiNiO2, and LiCoO2 is less than the theoretical specific capacity because significantly less than 1 atomic unit of lithium engages in the electrochemical reaction. Such an initial capacity value is significantly diminished during the first cycle operation and such capacity further diminish in successive cycles of operation. For LiNiO2 and LiCoO2 only about 0.5 atomic units of lithium is reversibly cycled during cell operation. Many attempts have been made to reduce capacity fading, for example, as described in U.S. Pat. No. 4,828,834 by Nagaura et al. However, the presently known and commonly used, alkali transition metal oxide compounds suffer from relatively low capacity. Therefore, there remains the difficulty of obtaining a lithium-containing electrode material having acceptable capacity without disadvantage of significant capacity loss when used in a cell.
Lithiated molybdenum oxides of the present invention have not been used in lithium ion batteries. Huang et al. in J. Electrochem. Soc vol. 135, page 411 (1988) describe lithium insertion in MoO2 to make a material characterized as LiMoO2. However, the structure of the material is different from that of the lithiated molybdenum oxides produced by the reduction processes of the invention. Tarascon in U.S. Pat. No. 4,710,439 discloses for use in a lithium metal battery a cathode material of nominal formula LixMo2O4 where x ranges from 0.3 to 2. The materials of Tarascon are prepared by ion exchange from a sodium material and have a monoclinic structure. In U.S. Pat. No. 4,251,606 to Haering et al., a battery is described that contains an anode of lithium metal and a cathode made of MoO2. During discharge, a portion x of lithium atoms can insert into the lattice of the cathode active material to form a substance with nominal formula LixMoO2, which, as in Huang, has a lattice structure like that of MoO2.